Cast shadows on some surfaces, but not others

Hi guys, I'm struggling to think of how to get this to work. I have a top-down space shooter game, and I want the ship to cast a shadow when over some surfaces - but not all.

The look I want is when the ship is moving over an asteroid, there should be a shadow, but when out in open space the shadow should be gone.

Any ideas? Perhaps I could do this with some sort of masking?

You can create an additional layer between the ship and asteroid. Create a shadow sprite (70% or so opacity) and pin it to the ship.

At beginning of layout -> [shadow sprite] is not visible

[shadow sprite] on collision with [asteroids] -> [shadow sprite is visible]

You can also use blend modes (assuming that your space background and the shadow are both black).

You can actually use blend modes without needing your space background to be entirely black.

here's a quick example I made. The asteroids and shadow are all on the 'shadowing' layer (with 'force own texture' set 'on'), and the shadow has a blend mode of 'source atop'.

Woah that's so simple, I would never have thought of using a blend mode for this. Thanks Sqiddster!